Hi Miguel,
The code in question is here:
github.com/NREL/ssc/blob/5ec04426cdfc4f83c397feb7c1ef66753ab9a70e/shared/lib_sandia.cpp#L424
The original source of that is Equation 1 on p. 14 of King, D.L.; Boyson, W.E.; and Kratochvil, J.A. (2004). Photovoltaic Array Performance Model. 41 pp.; Sandia Report No. 2004-3535. (
PDF 1.8 MB
)
It is also described on the Sandia PVPMC website:
pvpmc.sandia.gov/modeling-steps/dc-to-ac-conversion/sandia-inverter-model/
And, as you mention as Equation 12.3 on p. 74 of Gilman, P.; Dobos, A.; DiOrio, N.; Freeman, J.; Janzou, S.; Ryberg, D. (2018) SAM Photovoltaic Model Technical Reference Update. 93 pp.;
NREL/TP-6A20-67399. (
PDF 1.8 MB
).
I think there is a discrepancy between SAM and the documented equations. I will investigate and follow up when I learn more.
Best regards,
Paul.